Sir Alex Ferguson describes it as "the most embarrassing defeat of my management career", a result so shattering he took himself straight to bed that afternoon and hid his head under a pillow. "When my wife came in and asked what had happened I could hardly answer," he wrote later. "I was in total shock and completely gone."

Sir Alex Ferguson describes it as "the most embarrassing defeat of my management career", a result so shattering he took himself straight to bed that afternoon and hid his head under a pillow. "When my wife came in and asked what had happened I could hardly answer," he wrote later. "I was in total shock and completely gone."

Manchester United's manager was experiencing the effect known as a derby fever, the symptoms exacerbated by a 5-1 defeat by Manchester City that is still fondly remembered in the sky blue half of the city as the Maine Road Massacre. To this day United cringe when mention is made of Saturday morning, 23 September 1989.

The two clubs resume their on-field rivalry at Maine Road this morning after a break of four years. Absence, however, is unlikely to have made the heart grow fonder. The Manchester derby may not match the air of malevolence that swirls round its Glasgow counterpart, but the hurt is there for the loser as Ferguson's words betray. Meanwhile, the urgent need to settle scores has grown in City supporters' eyes in recent years as their fall and rise coincided with United's march towards six championships and one European Cup. Stand up if you hate Man U? How high do you want us to go?

But if Maine Road will be seething with jealous indignation today, the undercurrents will still not compare to the Manchester derby 93 years ago. Newton Heath and Ardwick, forerunners of United and City, had first met in the FA Cup in 1891 and had grown along largely religious lines (Catholic United, Church of England City). They had co-existed happily, however, until the latter were involved in the first great football bribes scandal at the end of the 1904-5 season.

An investigation led to five of City's best players, including the game's first superstar, Billy Meredith, being banned from playing for the club again. Worse, they eventually went across the city and formed the backbone of United's first championship side in 1907-08. You can imagine the emotions pulsing through the 35,000 crowd at Clayton that day when Meredith, Herbert Burgess and Sandy Turnbull appeared for the enemy in a derby for the first time. David Beckham will have it easy by comparison.

Turnbull, a character designed to give managers grey hair, would later become the first player to be sent off in a derby. He was also banned sine die by the Football Association for betting irregularities and was killed serving in the Manchester Regiment in the trenches of Arras in May 1917.

The inter-war period is known as the yo-yo years in Manchester; United were relegated in 1922, 1931 and 1937 and City in 1926 and 1938, the last downfall setting a precedent for their "cock-up" reputation because the Sky Blues managed to lose their top-flight status despite being the division's top scorers with 80 goals. But while the clubs were slipping past each other in the League they did manage their only FA Cup semi-final, City winning 3-0 in 1926.

The post Second World War period saw a thawing of relations when City allowed their neighbours to use Maine Road for an annual rent of £5,000 because Old Trafford had been destroyed by the Luftwaffe. City's reserves, meanwhile, played at The Cliff, which was United's training ground until their recent move to Carrington.

But if there was a cordial landlord-tenant relationship through the Fifties - an atmosphere helped by the appointment of a former City player, Matt Busby, as United's manager - that was shattered in May 1963. Denis Law had gone from Moss Side to Trafford Park via Torino and, as if that was not intriguing enough, the clubs were locked in a First Division relegation struggle, just a point apart at second and third bottom.

City were by far the better side in the early stages and went ahead after nine minutes through Alex Harley and had another "goal" disallowed for a hair's-breadth offside. Tempers were barely kept under control and before the interval Pat Crerand and Dave Wagstaffe were booked after an ugly confrontation.

Later it was revealed in the newspapers that Wagstaffe was laid out by an unnamed United player in the tunnel during half-time and perhaps that played a part in one of the most controversial climaxes to a Manchester derby. City were four minutes away from an important victory when Wagstaffe played a suicidal back-pass, Law nipped in and was brought down in the area by Harry Dowd. "It was a penalty," Law recalled in his autobiography. "The goalkeeper had hold of my legs, but I would never have scored. I was going away from the goal and had lost the ball. It was a lucky break for us."

It was an unlucky break for Dowd and his team-mates because Albert Quixall's penalty earned United a point that would mean the difference between their safety and City's relegation at the end of the season. Worse, as far as Maine Road was concerned, Law would be the outstanding player when United won the FA Cup final 3-1 against Leicester City a few days afterwards

City would gain ample compensation five years later when their 3-1 win at Old Trafford proved pivotal as they finished two points ahead of their great rivals to win the 1968 championship, but the ultimate revenge came in 1974.

Tommy Docherty had sold the now veteran Law back to Maine Road, but United were scrapping to avoid relegation when City arrived in April. Little happened until the 81st minute when Colin Bell found Francis Lee who, in turn, passed to Law. His position, with his back to goal near the penalty spot, was not promising but with typical impudence the former "King of Old Trafford" brilliantly back-heeled past a startled Alex Stepney.

Law made to celebrate, realised what he had done, then walked, head bowed, off the pitch and down the tunnel, leaving the game to go on for a few minutes before a second crowd invasion brought it to a premature end. His last touch in League football, which virtually ensured United's relegation, had been his saddest. "It was no more than a reflex action," he said, "and I felt sick. I have never felt so depressed in my life as I did that weekend."

United returned to the top division at the first attempt and in recent years the sights of their supporters have moved from Moss Side to down the M62. Liverpool are regarded as the principal rivals at Old Trafford now and most of the "anti" chants are aimed in that direction. "Are you City in disguise?" is occasionally chanted at particularly lamentable opponents, but the only other sign of tribal antipathy is the No 24 that hangs from a tier at the new Stretford End. It is assumed to refer to the years since the Sky Blue half of Manchester last won a trophy.

But if United's supporters have delivered the ultimate insult to their neighbours - virtually ignoring them - the same cannot be said for Maine Road, where the urge to stand up as a sign of antipathy to all things red has become a ritual. City's supporters once had every reason to believe the two clubs were neck and neck in terms of size and prestige (they even edged ahead in the Seventies) and have had to endure decline at home as prosperity has rained down on the enemy.

Which is why the walloping United took 11 years ago is so treasured by their supporters. The underdog took a huge bite at the giant's ankle that morning and even though City have not won a derby since and have endured a rout of their own, 5-0 in 1994, the memory has made the subsequent trips to the Second Division and back bearable. Just.

And the immediate consequences of that Maine Road Massacre? Within two months of masterminding a win that equalled City's record home victory in the fixture, Mel Machin was sacked and replaced by Howard Kendall after Joe Royle had turned down the opportunity. As for the man hiding under the pillow...